Wordsworth

What is the basic difference between the poetic creed of 'Classicism' and 'Romanticism' ?

I want to clear this term that what is “Classicism” and what is “Romanticism”. Difference between this is that a romantic poem will be about love towards people while classical will be more old fashioned and be about other things. The romantic era was not about love at all. In fact it had nothing to do with romance of the conventional kind. It was imaginative and more related to democracy and nature than anything else. Had relations to human life, and was highly philosophical. It was most definitely not about love. The Classical age on the other hand was the complete opposite to the romantic age in some respects. It had no real interest in nature as it exists naturally. Satire and realism was present, as well as a strong union with politics. It was highly critical, unimaginative and intellectual as opposed to the spontaneity of the romantic age. 

The basic difference between the classicism and romanticism is that the former is based on intellect and the latter is based on imagination.

 Why does Wordsworth say 'What' is poet ? rater  than Who is poet ?

There is difference between Who and What. Generally we use that who is poet ?? means we connect poets identity with it that This person is poet or that person is poet like example Wordsworth is poet is answer of this question but when we speak What is poet ??? We cannot find answer of this question easily because this question ties with inner quality or strength of poet. That what qualities poet has to write some good poems and then he gives reply that poet is one who is a man speaking to man, endowed with more lively sensibility because everyone cannot create lively images in front of readers who real poets can do.

What is poetic diction? Which sort of poetic diction is suggested by Wordsworth in his Preface?

From Wordsworth’s point of view Diction means choice of language, selection of words and arrangement of words with the help of emotions. He says that the language of poetry should be the language means language of day to day life who can understand by everyone but with the selection of proper words poet cannot use mean language or slang or wrong words for poetry. Language has power to create certain images in readers mind so use proper word so with the help of that word appropriate images can immerge for poetry. The word selected by the poet must fit to his imagination. If he is truly inspired, then his imagination will enable him to select from the language which is used by men in routine life.